1. Field of the Invention
The present invention is directed to a drywall fastener for use in a friable material, including a self-drilling drywall fastener to be used in drywall mounted to a stud member or the like.
2. Description of the Related Art
Because drywall is a friable material, mounting articles thereto can be difficult. In the past, at least three methods have been used. For light weight articles, small plastic expansion anchors have been used. These expansion anchors have typically required three steps to install: first, a hole is drilled into the drywall; second, the drywall fastener insert is driven into the drilled hole; and finally, a threaded fastener is advanced into the drywall fastener, spreading the drywall fastener into engagement with the drywall. However, expansion anchors can typically hold light loads only.
For heavy duty applications, toggle bolts have been used. While toggle bolts have been effective, they are also generally expensive because they involve parts which must move relative to one another. Toggle bolts also have been known to be difficult to install.
Self-drilling anchors for mounting heavier loads also have been used. These self-drilling anchors typically are installed by drilling into the drywall with the drywall fastener itself. The drywall fastener also includes threading having a high thread height to provide a high pullout in the drywall. Examples of self-drilling anchors include the drywall fastener sold under the trademark E-Z ANCOR manufactured by ITW Buildex, and those disclosed in U.S. Pat. Nos. 4,601,625, 5,190,425, and 5,558,479, all of which are assigned to the assignee of this application.
Self-drilling anchors have proved effective for holding higher loads when installed in drywall alone. However, in most cases the drywall is mounted to wood support members, or studs, that are unseen by the user, and typically the location of these support members are unknown and unchecked by the user. When a user of a typical self-drilling fastener attempts to install the drywall fastener in drywall at a location of a support member, the drywall fastener is unable to drill into the support member, causing the drywall fastener to spin in place so that the drywall fastener's high threading strips out the drywall, resulting in failure of the drywall fastener and creating an unsightly scar on the wall. Even if the drywall fastener is able to drill into the support member slightly, the anchors have been known to tightly engage the support member and break due to torsion on the anchor.
To install hooks, holders, or the like in drywall, many consumers use ordinary wood screws. While these may appear to work initially, the threads are generally too closely spaced and too low to achieve adequate contact with the drywall. Most commonly, these types of screws tend to bore a hole in the drywall, rather than gripping the drywall, leading to poor holding ability. Unless the installer locates a stud behind the drywall in which to drive the screw, an unsatisfactory result usually follows. While the use of anchors as described above generally overcomes this problem, existing anchors are usually unable to penetrate and attach to a stud or other structure behind the drywall, and require the multi-step installation process, i.e., initially centering and driving the anchor and then driving the proper fastener into the anchor to hold the object to be mounted to the wall. In some cases, the process may require pre-drilling of a pilot hole for the anchor, adding yet another step to the process. Also, it is important to utilize the proper screw or other fastener which properly fits and grips the anchor in order to obtain a secure installation. The provision of a suitable self-drilling drywall screw would greatly simplify this process.
What is needed is a self-drilling fastener for use in drywall that can be installed either in drywall, or in drywall and a support member, and is capable of handling a heavy load.